His revelation in a newspaper interview today will add to growing concern about the police investigation into the killing of the Brazilian electrician on Friday 22 July.

Sir Ian said he first learnt that the Brazilian was entirely innocent at about 10.30 the following morning, when one of his officers told him: "We have some difficulty here, there is a lack of connection" with the police inquiry into the terror attacks. "I thought, 'That's dreadful, what are we going to do about that?'"

His remarks came as The Independent on Sunday learnt that the Met Commissioner is to be questioned by the Independent Police Complaints Commission (IPCC) about a catalogue of errors in the police operation, and his own role as events unfolded.

The row over the shooting intensified further amid claims that the dead man's family had been offered £560,000 compensation by the police. However, the Home Secretary leapt to Sir Ian's defence, by insisting he was "very happy" with his and his force's handling of the affair.

The IPCC - which has the power to interview police under caution and to recommend criminal charges for misconduct - is due to question other senior officers who oversaw the surveillance operation that led to the killing.

An IPCC dossier leaked last week revealed that Mr de Menezes had done nothing to indicate he was a potential suicide bomber, and had calmly gone into Stockwell Tube station and boarded a train.

Despite initial claims from Sir Ian and eye-witnesses at the station that his behaviour was suspicious, the IPCC's evidence shows he had neither fled the police nor did he resist them. He was shot after an officer had grabbed him from behind and held him down.

Sir Ian's appearance in front of the IPCC would put their tense relations under even greater strain. The police have voiced their dismay at the leak of the IPCC files. Less than 90 minutes after the shooting, the Met Commissioner wrote to the Home Office asking for a delay in the IPCC inquiry because he believed the electrician was linked to the failed 21 July bombings in London. His request was rejected by the Home Office - but it was still three days before the inquiry began.

Two senior Brazilian legal investigators are due to arrive in London tomorrow to question the IPCC and the police. Mr de Menezes's parents are expected to visit London later this month and to visit the scene of his death.

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